1. Field of the Invention
The present invention relates to a fluorescent display apparatus constituting a large-screen display for use in a stadium or the like.
2. Description of the Prior Art
Large-screen displays are in use for displaying progress and result of sports events in such places as an outdoor stadium. A fluorescent display apparatus utilized in such a large-screen display is constructed of a large number of monochromatic illuminating tubes arranged in a matrix. FIG. 1 is a schematic diagram showing an internal arrangement of a prior art monochromatic illuminating tube.
The interior of the glass tube 1 is in a vacuum with air inside the tube evacuated through an exhaust hole 2. As a heater 3 heats up a cathode 4 surrounding the heater 3, thermoelectrons are emitted from the cathode 4. The thermoelectrons emitted from the cathode 4 is controlled in their flow by three types of grids 5, 6, 7 and allowed to bombard a fluorescent display portion 8 coated with fluorescent material. The fluorescent display portion 8 is applied with a high voltage and the part of the fluorescent display portion 8 bombarded by the thermoelectrons emits light. The grid 5 controls the quantity of the thermoelectrons emitted from the cathode 4, the grid 6 controls the diameter of the beam of the emitted thermoelectrons, and the grid 7 accelerates the emitted thermoelectrons. While potential for the grids 6, 7 is fixed, potential for the grid 5 is controlled, and thereby the quantity of the emitted thermoelectrons is controlled and the brightness of the fluorescent display portion 8 is regulated.
FIGS. 2 and 3 show a fluorescent display apparatus integrating a number of such monochromatic illuminating tubes therewith. On the apparatus, there are disposed the fluorescent display portions 8 of three primary colors, i.e., red (R), green (G), and blue (B) colors, suitably spaced apart in vertical and horizontal directions so as to be regularly distributed. Thus, with the potential of the grid 5 of each of the monochromatic illuminating tubes controlled, each of the fluorescent display portions 8 are controlled in their brightness and thereby a display is given with a desired color tone.
As a means to improve the resolution of such an apparatus provided with a number of monochromatic illuminating tubes, there is one using an illuminating tube being provided with a plurality of fluorescent display portions. However, since such an apparatus is of the structure that the cathode and grids must be provided for each of the fluorescent display portions, there are problems with it that the number of the component parts of the fluorescent display apparatus becomes larger, the internal structure becomes complex, and the power consumption becomes larger.